Bone replacement material, such as bone cements, can be used during certain medical treatments to help repair and/or reconstruct bone (e.g., fractured bone). The ability of certain bone replacement material to repair and/or reconstruct bone can be enhanced by the inclusion of bioactive agents (e.g., bone morphogenic protein), which promote the growth of bone.
To prepare bone replacement material, a powdery substance is generally combined with a liquid, and the resultant combination is mixed together and begins the curing process to form a bone replacement material dough or paste. The bone replacement material dough or paste can then be delivered to a treatment site (e.g., a fracture site) to help repair and/or reconstruct the bone.
The bone replacement material should be allowed to cure for a time so that the material is not too fluid, facilitates handling of the material and minimizes the risk of the material flowing undesirably outside the area of implantation. However, if the bone replacement material is allowed to cure too long before delivery, the bone replacement material will be too thick or even harden causing difficulties in working with or setting the bone cement. If left in the delivery device too long, the bone replacement material may completely harden rendering it useless.
Often the practitioner will determine the extent of cure of the bone replacement material by feel, involving kneading the bone replacement material as it cures and relying on judgment to assess properties of the bone replacement material such as viscosity (or firmness), tackiness, and smoothness (grittiness) before it is delivered to the implantation site. Assessment of these properties can be affected by environmental conditions, such as temperature and humidity.
Relying on subjective techniques such as feel to determine the extent of cure has the disadvantage that it is not always reliable, and it can be difficult to train new users of these techniques. Furthermore, the curing time of bone replacement material can be affected by variations in environmental conditions, such as humidity and temperature. Variations in the temperature of the practitioner's fingers as he kneads a sample of a bone cement can lead to variations in the extent of cure of that sample, relative to the extent of cure of the remainder of the cement which is to be used in the procedure. Also, variations in temperature and humidity will affect the perception of the tackiness of the cement.
Therefore, there is a need for bone replacement material delivery devices and methods that facilitate delivery of bone replacement material by allowing the user to more reliably monitor the cure of bone replacement material and reduce the need for the practitioner to rely on subjective techniques to monitor the cure of the bone replacement material.